docs: def list(self):
          """Lists all sessions in the store.
  
          .. versionadded:: 0.6
          """
          before, after = self.filename_template.split('%s', 1)
          filename_re = re.compile(r'%s(.{5,})%s$' % (re.escape(before),
                                                      re.escape(after)))
          result = []
          for filename in os.listdir(self.path):
              #: this is a session that is still being saved.
              if filename.endswith(_fs_transaction_suffix):
                  continue
              match = filename_re.match(filename)
              if match is not None:
                  result.append(match.group(1))
          return result